BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to communications systems. More particularly,
the present invention relates to a wireless transmission scheme for transmitting images
utilizing a cross layer method integrated the slice allocation and multiple modulation
and coding modes selection without the need of feedback channel.
[0002] EP1227684 discloses a method of encoding a digital video image signal comprising the steps
of segmenting the digital video image signal into at least a first and a second image
segment; identifying INTRA coded frames; encoding, for said INTRA coded frames, the
first image segment at a first quantisation level; encoding, for said INTRA coded
frames, the second image segment at a second quantisation level; and transmitting
a single encoded digital video signal comprising the first and the second image segments
over a communication network.
[0003] EP1775946 discloses remote editing system in which a remote editing apparatus edits hierarchically
encoded data, which forms an image stored in a main editing apparatus, via a network,
wherein the main editing apparatus transmits to the remote editing apparatus the hierarchically
encoded data that belongs to a predetermined hierarchical level; and the remote editing
apparatus accepts an editing operation that uses the transmitted hierarchically encoded
data, requests the main editing apparatus to transmit hierarchically encoded data
that is necessary for the generation of edited image data due to editing, and generates
edited image data by using the hierarchically encoded data that is transmitted from
the main editing apparatus in compliance with the request.
[0004] US2007002946 discloses a method for use in encoding multimedia content that identify one or more
first segments of encoded content having a quality level having a predefined relationship
with a first threshold limit; determine whether one or more additional segments having
quality levels that have a predefined relationship with a second threshold level and
are within predefined ranges from one or more of the first segments; re-encoding one
or more of the additional segments producing one or more re-encoded additional segments
having quality levels such that the re-encoded additional segments utilize fewer bits
than the one or more additional segments; and re-encoding one or more of the first
segments producing one or more re-encoded first segments such that the one or more
re-encoded first segments have quality levels that are greater than the quality levels
of the corresponding first segment.
[0005] Multicast and broadcast services (MBS) such as mobile IPTV are regarded as important
applications in WiMAX (Worldwide Interoperability for Microwave Access) networks.
It is desirable in a wireless network to simultaneously transmit the same video content
to a group of users to reduce bandwidth consumption compared with transmitting the
content to each user individually. However, the wireless environment is known to be
error-prone because of attenuation, shadowing, multipath fading, interference and
mobility of terminals. As a result, the channel characteristics vary in time and location.
Even under a connection-oriented network like WiMAX, the reliable transmission and
QoS guarantee for MBS is still a challenging task. Compared to unicast service, one
difficulty originating in MBS comes from the fact that the channel conditions between
the BS(Base Station) and each of the MSs (Mobile Station) in a multicast group may
differ and in the absence of feedback, which constrains the performance and deployment
of mechanism relying on the channel estimation.
[0006] By Using Adaptive Modulation and Coding (AMC) scheme, a WiMAX system can choose a
higher order modulation scheme or a lower order modulation scheme. In the area near
to the BS when SNR (signal-to-noise ratio) is good, the system can use the higher
order modulation scheme to maximize data transfer. In an area close to the cell boundary
with poor SNR or in a mobile system subject to multipath or shadowing interferences,
the system may step down to a lower order modulation, scheme to maintain the connection
quality and link stability. However, AMC alone is only suitable for unicast service
with dedicated feedback channel, there is no direct feedback channel defined for MBS.
Thus, the operating condition of individual receivers is unknown to the BS and therefore
adjustment on the source side during transmission are unavailable.
[0007] There are 3 conventional methods for the MBS in wireless transmission. Taking the
coverage with high priority, the first approach chooses the most robust modulation
for MBS in order to guarantee the reliable transmission in the whole cell. The disadvantage
is the poor performance for spectrum efficiency and the total number of supporting
services will be limited. The second trend is to deploy multiple bitstreams of the
same source sequence, generated with different parameters set and rate, the receiver
can switch from one of them to another based on the channel condition it detects.
The shortcoming is the redundancy traffic introduced will cause bandwidth waste. The
third one is selecting one group leader to report the channel quality through Channel
Quality Information (CQI) channel to the BS as the basis of adjustment, the problem
is the group leader can only represent the receivers near to itself, such setting
heavily penalizes those terminals exhibiting better or worse channel conditions.
[0008] The WiMAX standard supports an adaptive modulation and coding (AMC) scheme that enables
throughput optimization based on the propagation conditions. Under the same channel
bandwidth, the higher order modulation can achieve higher data rate during transmission,
but higher order modulation requires better channel conditions, so it has shorter
reliable transmission distance than lower order modulation..
[0009] It would be desirable to provide different types of video quality in term of display
region for the receivers located under different channel states inside the coverage
of BS. A desirable solution to overcome the above stated problems would improve the
transmission utility and spectrum efficiency for video MBS service in mobile WiMAX
network without the need of feedback channel.
SUMMARY OF THE INVENTION
[0010] The present invention provides a mechanism that combines the technology of slice
allocation/construction in application layer and modulation/coding selection in the
physical layer for video MBS service in the mobile WiMAX network. A balance of the
visual effect in the terminal and transmission efficiency in the system can be achieved.
Even in the situation that feedback is absent, terminals in the area with different
channel conditions can receive different quality of video in terms of display region.
[0011] In an exemplary embodiment, the present invention teaches a method of receiving an
image comprising the steps of receiving a first data representing a first region of
the image, wherein the first data is received at a higher order modulation scheme,
receiving a second data representing a second region of said image, wherein the second
data is received at a lower order modulation scheme. The exemplary method then discards
the second data in response to a quality indicator of the second data being below
a threshold or combines the first data and said second data to regenerate the image
in response to a quality indicator being above said threshold.
[0012] In a further exemplary embodiment, the apparatus comprises a display device wherein
the first data is displayed, wherein the first data represents a first region of the
image, if the quality indicator of the second data is below a threshold. If the quality
indicator of the second data is above the threshold, the device combines the first
data and said second data to regenerate the image and then displays the image.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
FIG. 1 illustrates an exemplary environment for transmission according to an exemplary
embodiment of the present invention;
FIG. 2 shows an illustrative diagram of a rectangular slice allocation pattern embodying
the principles of the invention;
FIG. 3 shows an illustrative portion of slice allocation patterns embodying the principles
of the invention;
FIG. 4 shows an illustrative sample downlink subframe in a WiMAX OFDM physical frame
in accordance with the principles of the invention;
FIG. 5 shows an illustrative flow chart in accordance with the principles of the invention.
FIG. 6 shows an illustrative block diagram of an apparatus operative to modulate and
prepare data for transmission on a wireless network according to an exemplary embodiment
of the present invention.
FIG. 7 shows an illustrative block diagram of an apparatus operative to demodulate
and prepare data for display on a display device according to an exemplary embodiment
of the present invention.
DETAILED DESCRIPTION
[0014] Other than the inventive concept, the elements shown in the figures are well known
and will not be described in detail. Also, familiarity with television broadcasting
and receivers is assumed and is not described in detail herein. For example, other
than the inventive concept, familiarity with current and proposed recommendations
for TV standards such as NTSC (National Television Systems Committee), PAL (Phase
Alternation Lines), SECAM (SEquential Couleur Avec Memoire) and ATSC (Advanced Television
Systems Committee) (ATSC) is assumed. Likewise, other than the inventive concept,
transmission concepts such as WiMAX (Worldwide Interoperability for Microwave Access),
eight-level vestigial sideband (8-VSB), Quadrature Amplitude Modulation (QAM), and
receiver components such as a radio-frequency (RF) front-end, or receiver section,
such as a low noise block, tuners, demodulators, correlators, leak integrators and
squarers is assumed. Similarly, formatting and encoding methods (such as Moving Picture
Expert Group (MPEG)-2 Systems Standard (ISOIIEC 13818-1)) for generating transport
bit streams are well-known and not described herein. It should also be noted that
the inventive concept may be implemented using conventional programming techniques,
which, as such, will not be described herein. Finally, like-numbers on the figures
represent similar elements.
[0015] The invention is proposed to improve the transmission utility and spectrum efficiency
for video MBS service in mobile WiMAX network. A cross layer method integrated the
slice allocation and multiple Modulation and coding modes selection are deployed in
the wireless environment without the need of feedback channel. One benefit of the
present invention is to provide different types of video quality in term of display
region for the receivers located under different channel states inside the coverage
of BS.
[0016] Turning now to Fig. 1, an exemplary environment for transmission (100) according
to an exemplary embodiment of the present invention is shown. The environment for
transmission (100) may comprise a base station, BS (110) or similar transmission point,
a first device, DEVA (120) located at a first distance (d1) from the BS, a second
device, DEVB (130) located a second distance (d2) from the BS, and a third device,
DEVC (140) located a third distance from the BS.
[0017] The BS (110) is operative to receive an image from a processor and transmit the image
to a plurality of devices (120, 130, 140) within the transmission radius of the BS
(110). However, as the distance between the BS (110) and each device (120, 130, 140)
varies, as does the propagation characteristics of the transmitted signal, as well
as the physical characteristics of the device, the ability for a device to receive
the transmitted signal at a certain bit rate, data rate, or compression scheme also
varies.
[0018] To overcome the above stated undesirable conditions experienced with wireless transmission,
the system according to the principles of the present invention is operative to divide
a coding image into coded slices, wherein each slice represents a region of the image.
The system them modulates each slice using a different modulation scheme such that
some slices may be received by MSs located in the entire cell boundary and some slices
may only be received by efficient MSs or MSs located in the area near the BS. The
slices and modulation schemes are chosen such that areas of interest of the image
are received by the maximum number of MSs and areas of the image that are not of interest
are received by a lesser number of MSs. Thus, the system eliminates the waste of bandwidth
associated with multicast transmission of the same content using different modulation
schemes, provides more data to those MSs able to receive less robust modulated signals
located in area with good channel conditions, and less data but still the data of
interest, to those MSs only able to receive a more robustly modulated signal.
[0019] Turning now to Fig. 2, an illustrative diagram of a rectangular slice allocation
pattern (200) embodying the principles of the invention. Video coding standards like
H.264/AVC allow dividing a coded picture to coded slices, which can be regarded as
a way to split a coded picture to independently decodable pieces. Considering the
watching behavior of human beings, people typically pay more attention to a particular
area in an image or video frame than to other areas in the same frame. Additionally,
typical picture composition places the focus on the central point in a picture. According
to one exemplary embodiment of the present invention, the original image (210) is
divided into 3 independent slices A (220), B (230), and C (240). The content in each
slice can be coded and transmitted as an isolated stream at differing modulation schemes.
The slices of the image deemed to be of greater interest to the user can be modulated
using a more robust modulation scheme, thereby ensuring that the maximum number of
MSs receiving the data of most interest. The slices deemed to be of less interest
are modulated using a less robust modulation scheme. The slice pattern however is
not limited to rectangular slices, and any number of slice patterns can be used, some
of which are depicted in Fig. 3.
[0020] Turning now to Fig. 3, an illustrative portion of slice allocation patterns (300)
embodying the principles of the invention is shown. The patterns for slices, in static
or flexible mode are unlimited and may vary according to image content or transmitter
processing power. Pattern I (310) for example, may be suitable for all types of central
focusing stream, pattern II (320) may be best suited for vertical partition matching
the TV program such as fashion show. For sports program, horizon partition like pattern
III (330) may be a better choice. The method to allocate isolated slices from a coded
picture or frame is out of the scope of this disclosure, any available patterns can
be the candidate. Additionally, the slice allocation pattern as well as the size of
the slices themselves may change based on the image content. For example, the image
processor may comprise an algorithm used to analyze the image and determine the areas
of interest to the user. For example, in a video transmission, areas that are the
most rapidly changing may indicate the areas of interest to the viewer. Thus, the
slices are made with the first slice comprising the areas of highest interest, or
movement, the second slice comprising the next highest areas of interest, and so on.
[0021] Thus according to an exemplary embodiment of the present invention, the proposed
region based modulation mechanism combines slice allocation and modulation mode selection
mentioned above. The priority of slice is defined in sequence as A>B>C, and each slice
is corresponding with a modulation/coding mode separately. Possible deployment scenarios
include, but are not limited to, QPSK, 16QAM, 64QAM etc.
[0022] Turning now to Fig. 4, an exemplary sample downlink subframe (400) in a WiMAX OFDM
physical frame in accordance with the principles of the invention is shown. The physical
OFDMA frame allocation can be implemented in the MBS data block inside the MBS zone.
The information of the block size and modulation coding mode are encapsulated in the
interval element (MBS-MAP). Isolated slices (A1, B1, C1) for MBS_Program1 are shown
in the representation in a broadcast/multicast session. The same processing is employed
for additional isolated slices (A2,B2,C2 and A3,B3,C3) in MBS_ Program 2 and MBS_
Program 3 respectively. According to this exemplary embodiment, each MBS program uses
the same allocation strategy. This is not mandatory however and the BS can choose
different allocation strategy based on the parameter of video traffic and the availability
of free bandwidth.
[0023] From a receiver aspect, the centralized region (slice A) only may be displayed if
the receiving device is located in the margin area of the cell and the other regions
(Slice B and C), cannot be effectively decoded. In this situation, the other slices
(Slice B and C) are discarded because of the transmission error or packet loss. The
leftover region may be displayed as black background, or slice A may be stretched
to cover a larger portion of the display area. Fore MSs within the middle distances,
a larger frame with slice A + slice B may be composed. For the nearest MS close to
BS, a full view of picture may be received as a result of better channel conditions
and the MSs ability to receive slices using all modulation schemes. According to the
exemplary embodiment of a sample deployment and visual effect as represented according
to Fig. 4, inside each slice, the coding and transmission is independent, so the decoder
based technology for error resistance like intra block refreshing, scalable video
coding and error concealment can be deployed, furthermore, some mechanisms in transmission
layer for error resistance like FEC(forward error correction) and ARQ (Automatic Repeat
reQuest) can also be introduce for QoS enhancement.
[0024] Turning now to Fig. 5, an illustrative flow chart (500) representing the reception
process in accordance with the principles of the invention is shown. Initially (510)
the apparatus waits for data to be received. Once data is received (520) the apparatus
decodes data 1 (53) according to a first modulation scheme, for example the most robust
modulation scheme being implemented. The apparatus then receives data 2 (540) and
then decodes data 2 (550) according to as second modulation scheme, such as the lower
robust modulation scheme being implemented. It should be noted that data 1 and data
2 may be received in the same physical frame by the receiver and subsequently separated
into separate data files, with each data file representing a different image slice.
The apparatus then measures the signal quality of data 2 (56) and compares this measured
signal quality to a threshold (570). The threshold represents the minimum signal quality
required for the data slice to be displayed. If the signal quality of data 2 exceeds
the threshold, the apparatus combines data 1 and data 2 (585) such that data representing
an image comprising the image slices represented by data 1 and data 2. If the signal
quality of data 2 does not exceed the threshold, the apparatus generates data representing
an image comprising the image slices represented by data 1 only (580). The data representing
the image is then sent to a display device (590) and the apparatus returns to the
start (510) to wait for the next data to be received.
[0025] Turning now to Fig. 6, a block diagram of an apparatus (600) operative to modulate
and prepare data for transmission according an exemplary embodiment of the present
invention is shown. The apparatus (600) includes a data processor (610), a modulator
(630), a memory (620) and a connection to a content source and to a transmitter suitable
for wireless transmission of the modulated data. The modulator (630) can be implemented
in either software or hardware, or a combination thereof. The memory (620) is operative
to store data and operating programs including programs previously described in exemplary
embodiments according to the present invention.
[0026] Turning now to Fig. 7, a block diagram of an apparatus (700) operative to demodulate
and prepare data for display on a display device according to an exemplary embodiment
of the present invention is shown. The apparatus (700) comprises a demodulator (710)
a data processor (720), a memory (730) and a connection to a receiver suitable for
receiving wireless transmission of modulated data. The demodulator (710) may be implemented
in either hardware or software or a combination thereof. The memory (730) is operative
to store data and operating programs including programs previously described in exemplary
embodiments according to the present invention.
[0027] Benefits of the present invention over the current state of the art include that
the number of slices in a frame and the size of each slice are determined by BS freely.
Furthermore, all slices for a picture can be encapsulated in the same physical frame,
thereby eliminating out-of-synchronization problems during the reconstruction of the
decoded slices in the receiver. Another benefit for mobile WiMAX is the ability to
support the mobility of terminal. For those moving terminals inside the coverage of
a BS, at a minimum they should be able to receive the content displayed in the central
slice and therefore be capable of displaying at least some content. For the situation
of handover, the mechanism of macro diversity and paging groups defined in the IEEE802.16e
standard can be deployed. Additionally, since the slice allocation pattern may be
kept unchanged during the life cycle of a program, bandwidth use can be further minimized
by eliminating the need to transmit duplicated information inside each frame (the
minimal frame slot in WiMAX network is 5ms), such notification of allocation pattern
can be done in the first several frames or periodically during transmission.
[0028] As described above, and in accordance with the principles of the invention, a receiver
determines equalizer lock as a function of the distribution of received signal points
in a constellation space, wherein different weights are given to different regions
of the constellation space. It should be noted that although the inventive concept
was described in terms of a weight value of zero (i.e., no weight) being given to
received signal points falling within an inner region and a weight value of one being
given to received signal points falling in an outer region, the inventive concept
is not so limited. Likewise, although the inventive concept was described in the context
of an outer region and an inner region, the inventive concept is not so limited.
[0029] In view of the above, the foregoing merely illustrates the principles of the invention
and it will thus be appreciated that those skilled in the art will be able to devise
numerous alternative arrangements which, although not explicitly described herein,
embody the principles of the invention and are within its spirit and scope. For example,
although illustrated in the context of separate functional elements, these functional
elements may be embodied on one or more integrated circuits (ICs). Similarly, although
shown as separate elements, any or all of the elements of may be implemented in a
stored-program-controlled processor, e.g., a digital signal processor, which executes
associated software, e.g., corresponding to one or more of the steps shown in, e.g.,
FIGs. 5 and/or 6, etc. Further, although shown as elements bundled within TV set 10,
the elements therein may be distributed in different units in any combination thereof.
For example, receiver 15 of FIG. 3 may be a part of a device, or box, such as a set-top
box that is physically separate from the device, or box, incorporating display 20,
etc. Also, it should be noted that although described in the context of terrestrial
broadcast, the principles of the invention are applicable to other types of communications
systems, e.g., satellite, cable, etc.
1. Verfahren zum Empfangen eines Bilds, wobei das Verfahren die folgenden Schritte umfasst:
Empfangen erster Daten, die ein erstes Gebiet des Bilds repräsentieren, wobei die
ersten Daten ein erstes Modulationsschema umfassen;
Empfangen zweiter Daten, die ein zweites Gebiet des Bilds repräsentieren, wobei die
zweiten Daten ein zweites Modulationsschema umfassen, wobei sich das erste Gebiet
und das zweite Gebiet gegenseitig ausschließen, ohne ineinander einen sich überschneidenden
Anteil des Bilds zu enthalten,
wobei das erste Modulationsschema robuster als das zweite Modulationsschema ist,
wobei das erste Gebiet einen höheren bewegten Anteil des Bilds als das zweite Gebiet
enthält; und
Verwerfen der zweiten Daten in Reaktion darauf, dass ein Qualitätsindikator der zweiten
Daten unter einem Schwellenwert liegt, und Kombinieren der ersten Daten und der zweiten
Daten in Reaktion darauf, dass der Qualitätsindikator über dem Schwellenwert liegt,
wobei der Schritt des Kombinierens ferner die folgenden Schritte umfasst:
Demodulieren der ersten Daten zum Erzeugen eines ersten demodulierten Signals, welches
das erste Gebiet des Bilds repräsentiert;
Demodulieren der zweiten Daten zum Erzeugen eines zweiten demodulierten Signals, welches
das zweite Gebiet des Bilds repräsentiert; und
Erzeugen eines kombinierten demodulierten Signals zum Koppeln an eine Anzeigevorrichtung,
wobei das kombinierte demodulierte Signal das erste Gebiet des Bilds und das zweite
Gebiet des Bilds umfasst.
2. Verfahren nach Anspruch 1, wobei der Schwellenwert eine minimale Signalqualität repräsentiert,
die erforderlich ist, damit die zweiten Daten angezeigt werden.
3. Verfahren nach Anspruch 1, wobei die ersten Daten und die zweiten Daten über eine
drahtlose Übertragung in einem einzigen Rahmen empfangen werden.
4. Verfahren nach Anspruch 1, wobei die ersten Daten mit einer ersten Häufigkeit übertragen
werden und die zweiten Daten mit einer zweiten Häufigkeit übertragen werden.
5. Verfahren nach Anspruch 1, wobei die ersten Daten in Übereinstimmung mit einer ersten
Datenrate moduliert werden und die zweiten Daten in Übereinstimmung mit einer zweiten
Datenrate moduliert werden.
1. Procédé de réception d'une image, le procédé comprenant les étapes suivantes :
réception de premières données qui représentent une première zone de l'image, les
premières données comprenant un premier schéma de modulation ;
réception de deuxièmes données qui représentent une deuxième zone de l'image, les
deuxièmes données comprenant un deuxième schéma de modulation, la première zone et
la deuxième zone s'excluant réciproquement sans qu'une partie de l'image soit en chevauchement
dans l'une et l'autre,
le premier schéma de modulation étant plus robuste que le deuxième schéma de modulation,
la première zone contenant une plus grande partie animée de l'image que la deuxième
partie et
rejet des deuxièmes données en réaction au fait qu'un indicateur de qualité des deuxièmes
données est inférieur à une valeur seuil, et combinaison des premières données et
des deuxièmes données en réaction au fait que l'indicateur de qualité est supérieur
à la valeur seuil, l'étape de combinaison comprenant en outre les étapes suivantes:
démodulation des premières données pour générer un premier signal démodulé qui représente
la première zone de l'image;
démodulation des deuxièmes données pour générer un deuxième signal démodulé qui représente
la deuxième zone de l'image et génération d'un signal démodulé combiné pour couplage
à un dispositif d'affichage, le signal démodulé combiné comprenant la première zone
de l'image et la deuxième zone de l'image.
2. Procédé selon la revendication 1, la valeur seuil représentant une qualité de signal
minimale requise pour l'affichage des deuxièmes données.
3. Procédé selon la revendication 1, les premières données et les deuxièmes données étant
reçues dans une trame unique via une transmission sans fil.
4. Procédé selon la revendication 1, les premières données étant transmises avec une
première fréquence et les deuxièmes données, avec une deuxième fréquence.
5. Procédé selon la revendication 1, les premières données étant modulées selon un premier
débit de données et les deuxièmes données, selon un deuxième débit de données.